The invention concerns a perforating apparatus for producing openings in a peripheral surface of a substantially elongate, cylindrical object, in particular a cigarette, comprising a light source for producing at least an energy-rich light beam by means of which the openings can be formed in the object, an operative zone which can be produced by a guidance tracking means for guidance tracking of the light beam and within which the light beam acts on an object moving through the operative zone for forming the openings therein, rolling means for producing a rotary movement of the objects about their own longitudinal axis while the objects move through the operative zone in order to expose the peripheral surface to the light beam, and transport means for conveying the object through the operative zone.
Apparatuses for providing perforations in elongated cylindrical objects are known from the prior art, but none have the advantages provided for by the current invention. Such apparatuses serve in the prior art, in particular in the tobacco-processing industry, to provide smoking articles, in particular cigarettes, with a zone affording the desired permeability for air. This zone involving the desired permeability for air is usually formed in a sheathing material strip of the smoking article or cigarette. That perforation in the peripheral surface of the smoking article, which is mostly provided in the region of the tip end, is of significance in the cigarette industry as smoking articles which are perforated in that way provide that cool air from the ambient atmosphere is added to the smoke when the smoker draws on the smoking article or cigarette. That cool air serves in turn to influence the proportions of nicotine and condensate in the smoke.
In regard to forming perforations in the peripheral surface of a substantially elongate, cylindrical object, in particular a cigarette, a fundamentally important consideration is that the perforation can be produced uniformly and reproducibly. For that purpose, lasers are mostly used as the light source in the state of the art. In that situation, the size of the holes forming the openings in the peripheral surface can be varied by means of suitable focusing of the laser beam.
In the state of the art, rolling drums and the like are mostly used as the transport means for the cigarettes to be perforated. Those rolling drums convey the cigarettes with their axis disposed transversely, through the point of impingement of the laser beam. In order to achieve a perforation effect not only at one location on the peripheral surface but in order to produce the perforation effect at least over a part of the periphery, the cigarette, while it is being conveyed with its axis in a transverse position by the rolling drum serving as the transport means, is usually rolled by means of rolling means which engage the cigarettes from the side in opposite relationship to the rolling drum. It is important in regard to rolling the object between two surfaces in that way that the cigarette or the smoking article is subjected to pressure forces and the like, to the minimum possible extent. For, forces of that kind have an adverse effect on the quality of the cigarette.
A known perforating apparatus which operates with a laser is shown for example in U.S. Pat. No. 5,148,818. The reference discloses a perforating apparatus using a plurality of rollers as the transport means for the cigarettes. A conveyor belt serving as the rolling means rotates on those rollers so that the cigarettes are disposed between the conveyor belt and the rollers. Because the conveyor belt moves at a different speed from the rollers, the cigarettes which are disposed between the conveyor belt and the rollers are caused to perform a rotary movement about their own axis. In addition, disposed at the centre of one of the rollers is a laser with a laser beam which also rotates and which burns the perforations into the rotating cigarettes.
A disadvantage with this prior art device is that the laser beam must also rotate with one of the rollers and that the rotary movement of the laser beam must be exactly matched to the conveying movement of the cigarettes. This arrangement involves a very high level of technical complication and expenditure to operate and thus a very high level of cost.
A further device is known from DE 33 10 930. This reference discloses a perforating apparatus in which, with the cigarettes circulating on a drum, the appropriate perforations are formed in the sheathing or casing of the cigarettes to be perforated by means of a heart-shaped reflector in which a laser beam circulates.
This device similarly suffers from the disadvantages of requiring a very high level of technical complication and expenditure, as it is necessary to rotate the laser beam in the heart-shaped reflector. This must be done while simultaneously rotating the cigarettes synchronously with the rotational movement or reflection of the laser beam to the correct position so that the perforations are formed uniformly in the casing of the cigarettes. This synchronisation is difficult and costly to maintain.
Still a further device is known from DE 34 31 051. In that publication, a laser is also connected to a complicated reflector arrangement. In this case also, the laser beam is guided by way of a highly complicated arrangement of mirrors and rotating reflectors to the location to be perforated, on the casing of the cigarette that rotates on a roller. This apparatus is also extremely complicated and expensive and in addition can only be synchronised with a very great deal of difficulty, suffering from the same disadvantage of cost and complexity of the earlier cited devices.
A further device is known from DE 34 31 067. This reference represents a combination of the teachings of the two previously disclosed references. It therefore also suffers from the disadvantages described hereinbefore with reference to the last two publications.
A further perforating apparatus is known from DE 42 18 266. In this apparatus, the cigarettes that are being conveyed are disposed between a plurality of rollers so that they can be rotated between these rollers. Carried on the conveyor roller for the cigarettes is a polygonal mirror which projects a laser beam onto the cigarettes to be perforated.
This arrangement also suffers from the disadvantage that the cigarettes must be perforated by means of an expensive and complicated polygonal mirror configuration. Furthermore, this apparatus suffers from the disadvantage that the cigarettes are respectively disposed between three rollers so that the individual cigarettes are subjected to the effect of very high forces which can have a disadvantageous effect on the condition of the cigarette.
Finally, DE 27 51 522 discloses a further perforating apparatus. In this perforating apparatus, the cigarettes are caused to rotate about their own axis between a rolling drum and a so-called rolling block. During the rotary movement of the cigarettes, a laser beam perforates the cigarettes. As, during their rolling movement between the rolling drum and the rolling block, the cigarettes are advanced in the rolling passage formed in that way, relative to the laser, the laser beam is guided in such a way as to track the cigarette which moves in the rolling passage. That guidance tracking action for the laser beam is performed in this prior-art perforating apparatus by means of a drum, which at its periphery carries a plurality of mirrors. This rotating polygonal mirror arrangement must be activated synchronously with the movement of the cigarettes in the rolling passage formed by the rolling block and the rolling drum. This state of the art therefore requires a very high level of synchronisation and precision in order to be able to achieve a satisfactory perforating result.
Besides the disadvantages just referred to above, the device further suffers from the disadvantage that the perforations can only be formed in the cigarette during half a rotation of the cigarette about its own axis. In that state of the art, therefore, the cigarette is completely perforated by means of the laser beam. It is only in that way that perforation of the entire periphery of the cigarette can be effected in the rolling passage. Piercing the cigarette as a whole in that way however is often not desirable in production of the cigarette as it has adverse effects on the quality of the cigarettes produced.
Therefore, the object of the present invention is to avoid the above-mentioned disadvantages which occur in the state of the art, and to provide a perforating apparatus a minimum level of technical complication and expenditure, and without requiring complicated synchronization makes it possible to perforate the entire periphery of the elongate, cylindrical objects, in particular cigarettes, in a cost effective manner. In that respect, the invention further seeks to ensure that the forces acting on the objects during the perforating operation, in particular forces due to the rolling means, are kept as low as possible.
In a perforating apparatus of the kind set forth in the opening part of this specification, the foregoing object is attained in accordance with the invention in that there is provided a stationary light-refracting means through which the light beam serving for perforation is passed before reaching the actual operative zone, so that, when the light beam is caused to track the object which is passing through the operative zone, the light beam remains focused substantially everywhere within the operative zone.
The advantages of the invention are in particular that the light-refracting means according to the invention makes it possible to eliminate complicated and expensive mirror structures and complicated and expensive rotating mirrors. By virtue of the invention, it is sufficient to have a stationary light-refracting means through which the light beam passes before reaching the operative zone and through which the light beam passes during the complete movement of the light beam by virtue of the guidance tracking means through the operative zone.
In accordance with the invention, it is particularly advantageous if the light refracting means is a focus-corrected lens (F-theta lens). The invention can be carried into effect in a particularly simple fashion by means of such a lens. A lens of that kind can be arranged preferably with its main plane parallel to the path of transportation movement of the objects to be perforated, in such a way that the lens lies in the path of the light beam to the operative zone, throughout the entire guidance tracking region of the light beam. In that case, the focus-corrected lens (F-theta lens) ensures that the light beam, and in particular a laser beam, passes onto the object or on the peripheral surface of the object to be perforated, in a condition of being focused by the lens at each respective location within the operative zone, throughout the entire guidance tracking movement for covering the operative zone.
That is due to the fact that the focus-corrected lens (F-theta lens) has the same focal distance available over its entire width along the main plane. In the case of a lens of that kind therefore, the light beam or laser beam can be displaced over the main plane, without the focal distance and thus the focus of the laser beam that passes through such a lens being changed. Therefore, by means of such a lens, the laser beam can be caused to follow the object that moves with a rolling motion on the transverse conveyor, without the laser beam being de-focused.
Lenses that afford the above-mentioned advantages of the invention can be obtained for example from the company Laser Components GmbH of Olching, Germany. In that respect, planoconvex lenses, meniscus F-theta planar field lenses and spherical ZnSe-F-theta planar field lenses, which are products offered by that company, are particularly advantageous.
In a particularly preferred embodiment of the invention the transport means is in the form of a transverse conveyor. In embodiments of the invention, the transverse conveyor can be in the form of a belt conveyor or in the form of a rolling drum. The transverse conveyor conveys the objects to be perforated, in particular cigarettes, with their longitudinal axes disposed transversely with respect to the direction of conveying movement.
The objects to be perforated are moved into the operative zone of the light beam by means of such a transverse conveyor. Then, within the operative zone of the laser beam, which is produced by the light beam guidance tracking means, the perforations or openings can be formed in the peripheral surface of the object that moves in axially transverse relationship through the operative zone. While the object is moving through the operative zone, the light beam and in particular the laser beam is caused to follow it by means of the guidance tracking means which are preferably in the form of pivotal mirrors. It is therefore ensured that the objects to be perforated are engaged by the light source during the entire period for which they are in the operative zone, so that during the entire period for which the objects are in the operative zone, perforations can be formed in the peripheral surface of the object.
If now perforations are to be formed in the object over the entire periphery thereof, then the object must be rotated while it is moving through the operative zone. That is achieved by means of the above-mentioned rolling means. The rolling means cause the object to perform a rotary movement about its own axis. In a preferred embodiment of the invention, the rolling means is in the form of a co-operating counterpart rolling surface which is disposed opposite to the transverse conveyor. That counterpart rolling surface can be in the form of a counterpart rolling belt or in the form of a counterpart rolling drum. In such an arrangement, the directions of conveying movement of the counterpart rolling surface and the transverse conveyor can be opposite or in the same direction. When the counterpart rolling surface involves a conveying movement component in the same direction, the object to be perforated is accelerated in the rolling motion, in the area in which the transverse conveyor and the counterpart rolling surface co-operate. When the counterpart rolling surface and the transverse conveyor involve conveying movement components in opposite directions, the object to be perforated is retarded or slowed down in the area in which the transverse conveyor and the counterpart rolling surface co-operate. In both cases however, the object is caused to perform a rolling movement on the transverse conveyor. That rolling movement can occur stationarily relative to the transverse conveyor in a recess provided for the object. The rolling movement however can also be produced in a rolling region which is provided for that purpose on the transverse conveyor. In the latter case, it is preferred if raised portions on the transverse conveyor respectively delimit the rolling region provided on the transverse conveyor. In that way, at the moment of co-operation of the counterpart rolling surface and the transverse conveyor, the object to be perforated moves from one raised portion defining the rolling surface to the other. When, in such an embodiment, the entire periphery of the object to be perforated is perforated, the object is moved between the two raised portions once about its axis. In that case, the light beam or laser beam for perforating the object is then caused to follow the object corresponding to the movement of the object over the rolling surface at the transverse conveyor in order to perforate the object entirely around its periphery.
In another preferred embodiment of the invention, the objects to be perforated are disposed in a stationary manner, relative to the transverse conveyor, in openings or recesses in the transverse conveyor. The rolling means is formed not just by a counterpart rolling surfacexe2x80x94as described hereinbeforexe2x80x94but there is also provided a further rolling surface in opposite relationship to the counterpart rolling surface. The further rolling surface can also be in the form of a rolling belt or rolling drum. That second rolling surface engages the objects to be perforated, in the operative zone, that is to say in the area of co-operation between the counterpart rolling surface and the transverse conveyor, from the side which is opposite to the counterpart rolling surface. This embodiment therefore involves a co-operation in the operative zone as between the counterpart rolling surface and the rolling surface. In that respect, it is particularly preferred if the rolling surface has a conveyor movement component which is opposite to that of the transverse conveyor while the counterpart rolling surface has a conveying movement component which is in the same direction as the transverse conveyor. In that way, the object to be perforated and in particular the cigarette is acted upon in the operative zone by respective oppositely directed conveyor forces in diametrically opposite relationship so that the cigarette is turned in the opening or recess on the transverse conveyor.
A further preferred embodiment of the present invention is distinguished in that the rolling means is an integral component of the transport means. With this embodiment, it is further preferred if the transport means is a transverse conveyor on which the objects are conveyed in axially transverse relationship, wherein the transverse conveyor has receiving means for receiving the objects. In this embodiment, these receiving means are preferably distinguished in that they are rotatable for producing the rotary movement of the objects about their own longitudinal axis. In this case, the receiving means are preferably in the form of troughs or depressions which are preferably subjected to the action of suction air in order to hold the objects in the troughs, even during the rotary movement of the troughs or the objects about their axis. The advantages of this embodiment are in particular that each individual object can be precisely rotated, by means of this structure. In this embodiment, therefore, no serious inaccuracies are involved in the rotary movement of the object. In this way, therefore, by virtue of this construction, the perforations can be formed in the objects precisely at accurately predeterminable points. This embodiment further has the advantage that, due to the fact that each object is disposed in its own receiving means, there is no possibility whatsoever of the objects interacting with each other, so that this embodiment is distinguished by a particularly high degree of reliability.
In a further preferred embodiment of the invention, the above-mentioned receiving means are mounted rotatably directly on a transport drum. In this arrangement, the objects are preferably transferred from a feed conveyor drum directly to the transport drum, passed through the operative zone of the light beam, and transferred directly from the transport drum to a discharge conveyor drum or another working device. In this way, by means of this embodiment, the roller of the transport means can be optimally combined with that of the rolling means so that this arrangement overall also provides for a reduction in the structural length of a perforation apparatus of such a design configuration. Applicants: Manfred Dombek, et al.
In a further preferred embodiment of the present invention, the transport drum has a given pitch spacing or division, wherein the objects are rotatable once about their axis within a rotational movement of the transport drum through one pitch division. In that way, the complete perforation can be produced within the rotational movement of the rotary drum through one pitch division. As a result, the necessary laser beam tracking movement is also reduced to a necessary minimum.
This embodiment is advantageous because when the light source acts on the objects to be perforated, from the interior of the transport drum, the light source also has, during the tracking movement of the light beam, a light path between itself and the objects, which remains approximately the same, as the objects are moved on a circular trajectory.
A further preferred embodiment of the invention has, along the periphery of the transport drum, two rows of receiving means which are disposed in mutually opposite mirror-image relationship, at a given pitch spacing relative to each other. In this way, it is advantageously possible simultaneously to perforate double the number of objects if the light source is also divided, for example, by a beam splitter or if the arrangement has two light sources.
A further preferred embodiment of the invention is shown in which each two receiving means are disposed in mirror-image opposite relationship and a rotatable by means of rotating means. In this embodiment, the rotating means respectively include pinions which are fixed to the receiving means, the pinions respectively meshing with a gear arranged on a common drive shaft. In this way, the drive for two oppositely disposed receiving means is advantageously effected by a single drive shaft.
With this embodiment, it is further preferred if the drive shaft is drivable by a control means which is arranged at one of the end insides of the transport drum and which by way of a gear drives a pinion on the drive shaft. This embodiment is also advantageously distinguished by virtue of being of a small structural size, insofar as the control means are also disposed within the transport drum. In that case, it is further preferred if the control means is a lever guided in a stationary control cam, the control cam further preferably being in the form of a U-shaped groove in one of the end wall insides of the transport drum. It is advantageously possible, by means of such a U-shaped groove, for the lever serving as the control means to be precisely guided at any time.
In a further preferred embodiment of the present invention, the above-mentioned receiving means of the row thereof, which are adjacent along the periphery of the transport means, are each provided with their own respective rotating means or drive means. In that case, it is further preferred if receiving means which are in adjacent relationship along the periphery of the transport drum each have their own control means. Thus, in this embodiment, each receiving means which is adjacent along the periphery is advantageously moved separately from each other and in a controlled and deliberate fashion.
A further preferred embodiment of the invention is distinguished in that the receiving means are rotatable by the rotating means, in such a way that the rotary movement of the objects about their longitudinal axis occurs at least during the movement of the objects through the operative zone. In this case, it is further preferred if the rotary movement of the objects takes place substantially only during the movement of the objects through the operative zone. In this way, the objects are loaded by the rotary movement, only during their movement through the operative zone. In that respect, it is further preferred if the rotary movement of the objects about their longitudinal axis takes place uniformly, that is to say preferably at a steady angular speed, during the movement of the objects through the operative zone. In this way, the objects can be rotated through 360xc2x0 at a constant rotary speed during their movement through the operative zone, and they can then be brought to a halt again. In that respect, it is further preferred if the objects can be accelerated to the necessary rotary speed before reaching the operative zone and can be decelerated again to their rest condition after reaching the end of the operative zone. In this case, the acceleration and deceleration movements preferably take place substantially linearly.
Further preferred embodiments of the invention are set forth in the appendant claims.